You are an angel on earth! It is time to focus on you and your own children. He is your boyfriend and does sound like he is using you.
Maybe you should suggest he move back to his own home and you start living your life again. I assume you are getting unemployment--I would also seek assistance with whatever you can to make it work for you and YOUR children.
You said your relationship was rocky to begin with and sounds like that has worsened.
It is time to stand up and take charge of your life--may be hard, but if you can go through what you have over last several months--you can do anything!